History shows weather variables from a specific time in the past. Historical data and diagrams are available for hours, days, months and entire years, and can be selected for a specific period. They are used to reproduce weather conditions at a specific location during a specific time, using the most common variables, such as temperaturerelative humidity, precipitationwindradiation, sunshine  and pressure. Other parameters are available on request. History information is available through measurements for some locations, where sufficient measurement data are available, and through simulations for the entire world.

An example of a History feature is the weather archive that is based on simulations

Our historic weather data is derived from simulations. 
As a general (but not universal) rule of thumb, it can be said that these data are more precise for a particular location than data from a measurement station located more than 20-50 km away. In variable terrain, that distance may be (much) less.

The process and quality of these data are described on the following pages:

> Simulation



> Verification



> Data availability



There are a few “difficult" situations where the data will be less able to reproduce local reality : 
- In terrain with very pronounced changes of altitude (e.g. mountains), land cover (e.g. forest, grass, fields, cities, rocks…), or surface (land, water). 
- For precipitation in tropical areas with large percentage of convective precipitation: there, simulations will underestimate precipitation, sometimes substantially. 
- For purposes with very high precision requirement such as construction of  renewable energy generators, such as wind or solar power, or building management.
For those  “difficult” situations, we recommend using additional research using available measurement data.